Our present invention relates to a canned motor pump of the type in which the motor includes a carrier for the stator winding and, more particularly, wherein the fluid side of the pump is separated from the stator by a motor can, i.e. a pump in which the rotor and impeller on the one hand are separated from the stator winding on the other hand by a motor can.
Can-motor pumps usually are asychronously operated with three phase or simple alternating current energization since asynchronous motors are well developed and are characterized by a compact construction and a high degree of reliability in low power and medium power applications, the efficiency of asynchronous motors is, however, insufficient. It is also a drawback that with small asynchronous machines a disproportionally large portion of the cost of the motor is in the electronics for stepless motor control. Canned motors have the advantage that the electrical input side of the motor is hermetically sealed by means of the motor can from the rotating parts and the medium displaced by the pump.
In conventional canned motor pumps with asynchronous drives, the stator winding is usually wound in an insulated stator sheet stack and shoved with the stator sheet stack onto the metallic can.
Conventional commutated drive canned motor pumps may have the stator winding wound directly on the motor can. A drawback with such canned motor pumps is that in case of a defect in the pump, the entire stator winding must be dismounted from the can and generally cannot be reused. To the extent that the stator winding is adhesively or otherwise bonded to the motor can, both the winding and the can must be discarded or scrapped.
It is, therefore, the principal object of the present invention to provide an improved canned motor pump of lower fabrication cost and free from the drawbacks of earlier systems.
Another object of this invention is to provide a canned motor pump which is economical, easily disassembled and wherein the stator winding or coils need not be discarded or scrapped in the case of disassembly for repair purposes.
Still another object of this invention is to provide a canned motor pump whereby drawbacks of conventional motor-driven pump systems are avoided.
These objects and others which will become apparent hereinafter are attained, in accordance with the invention, by providing around the motor can and fitted over and onto the motor can a cylindrical winding carrier which receives the stator winding and at least partly surrounds the cylindrical part of the motor can. With this construction it is possible to remove the stator winding with the winding carrier which can be left in place or to shove the carrier with the stator winding onto the mounted motor can and thus to reuse the carrier and the stator winding without having to dismount the motor can and without damaging the latter or the coils.
The stator winding can be premounted upon the carrier and especially can be baked thereon and thus fixed in position on the winding carrier. The winding carrier can then be shoved onto the cylindrical portion of the motor can and can be secured by fastening means on the motor can or on the pump housing and thereby held in position.
The winding carrier advantageously rests with its cylindrical inner surface on the cylindrical outer surface of the motor can, thereby providing a thermally conductive bond between the winding carrier and the motor can.
The winding carrier can be composed of a temperature resistant synthetic resin material, e.g. a polycarbonate, which can lead to a particularly low overall weight of the pump.
To the extent that the motor is an electrically commutated motor, the permanent magnets for torque transmission from the stator to the pump rotor can be spaced equidistantly around the rotor axis on the side of the rotor turned toward the can. The commutation can be effected by electronic circuitry within the pump casing or on the latter with the heat generated by the commutating electronics being transmitted by thermal bridges to the casing and ultimately the displaced medium. For the detection of rotor position or rotor speed, sensors can be integrated into the stator winding affording still further cost savings.